Various crane systems are known from the prior art which offer certain advantages depending on the field of application. Revolving tower cranes having trolley booms are thus known in which the boom always adopts a horizontal position and in which the load can be traveled over the total boom length with the aid of a trolley. This provides the advantage that the suspended load can be moved particularly close to the tower.
In contrast, there are tower cranes having luffing booms which are also called variable booms. The luffing boom is fastened by a joint to the crane tower beneath the tower top and is variable in height via a boom guy rope. Such cranes do not have a trolley; the load is transported in the boom direction solely via the lifting and lowering movement of the boom. The named crane design above all provides advantages with tight space requirements since the boom can simply be “retracted” to avoid collisions with obstacles. In addition, the load can be raised to greater heights due to the steeper boom position.
An increasingly high degree of flexibility is in particular expected of mobile construction cranes which have a travelable, full-fledged revolving tower crane with a trolley boom. This crane structure is frequently intended to operate under complex spatial conditions at the construction site so that the aforesaid advantages of the luffing boom system are of great interest.
In the past, it has already been endeavored to merge the two proposed crane systems with one another. The advantages of the two different crane systems should in particular be combined in a single crane system.
A revolving tower crane is known from DE 1 171 132, for example, which has a retractable boom and a trolley guided thereat. The trolley is latched to the tip of the boom for the operation as a luffing boom. Any desired incline is hereby allowed for the boom system without the trolley leaving its position at the tip.
The support of the trolley at the boom tip, however, increases the unladen weight torque of the boom system and consequently reduces the possible peak payload in luffing operation. In addition, hoist rope length is lost due to the reeving of the hoist rope which can actually be needed with steep boom positions.
It is the object of the present invention to provide a crane or a method of operating a crane with which the initially named problem can be overcome.
This object is achieved by a method of operating a crane in accordance with the features of claim 1. Advantageous embodiments of the method in accordance with the invention are the subject of the subordinate claims dependent on the main claim.
Claim 1 therefore proposes a method of operating a crane having a luffable crane boom and having a trolley travelable at the crane boom. The crane configuration on the one hand allows crane operation in the luffing mode and on the other hand an operation in the trolley mode. The crane operator can selected the ideal crane mode based on the application and can convert the crane between the individual modes by carrying out the method.
The crane is, for example, configured as a revolving tower crane, in particular as a mobile construction crane, which comprises a luffing boom having a travelable trolley.
Previously known designs from the prior art propose fastening the trolley to the boom tip for the luffing mode and to let off the crane hook from the trolley. The present invention now takes a path which differs in decisive points. In accordance with the invention, the reeving of the hoist rope at the boom system is varied so that a luffing operation of the crane is made possible. The deflection of the hoist rope from the boom to the crane hook thus takes place independently of the trolley.
The re-reeving above all opens up the possibility of positioning the trolley at any desired position of the crane boom during the luffing operation. A support at the boom tip is no longer absolutely necessary, from which certain advantages result. For example, a positioning of the trolley close to the tower can have a favorable effect on the unladen weight torque of the crane.
Furthermore, not only an increase in the peak payload can be achieved during the luffing mode by a favorable choice of the fixing position, but also an increase in the effective crane outreach. The travel path of the trolley to the boom tip is limited as a rule by the technical circumstances so that the theoretically maximum outreach of the crane could not be ideally exploited either in the trolley mode or in the luffing mode. Due to the re-reeving in accordance with the invention, this disadvantage can be avoided during the luffing mode and the effective crane outreach can be increased.
It has been found to be particularly advantageous if, due to the re-reeving, a change is made between a single-line operation in the luffing mode and a multi-line operation, in particular a dual-line operation, in the trolley mode. Due to the re-reeving of the hoist rope into a single-line operation, additional hoist rope length can be gained which is in particular advantageous with steep boom positions in the luffing mode.
The hoist rope is beaten up to the boom system at the end side during the trolley mode. To change the reeving, it may be advantageous for the fixing point of hoist rope to be released for the crane operation in luffing mode and for it to be beaten up to a lifting hook or to be latched thereto. The crane is then operated in single-line operation. It is particularly expedient if a separate lifting hook is available for the luffing mode.
In a particularly advantageous embodiment, the trolley and/or the used crane hook/hook block of the trolley mode is latched to the boom or to the trolley for operation in the luffing mode. Since the latching of the trolley does not necessarily have to take place at the boom tip in the present invention, a latching positions is selected which is ideal with respect to the unladen weight of the trolley, which is expediently spaced apart from the boom tip and which reduces the unladen weight torque at the boom tip. A latching of the trolley close to the pivot connection point of the boom is particularly advantageous.
In this case, it can be advantageous to use an anyway present transport position or dismantling position for the trolley to latch it to the boom during the luffing mode. This transport position or dismantling position for the trolley is as a rule arranged in the region of the boom pivot connection point.
It is expedient in an advantageous embodiment of the invention to use a rope reeving pulley provided during the trolley mode as a deflection pulley during the luffing mode. The rope reeving pulley is as a rule arranged at the boom tip and serves the fixing or support of the hoist rope at the boom tip during the trolley mode. It is conceivable that the position of the rope reeving pulley for the luffing mode is directly spatially varied to be able to ensure an ideal deflection of the hoist rope.
It is of advantage for the re-reeving for the boom tip to be let down close to the ground. In this case, the re-reeving can be carried out comfortably and without any great effort from the ground by the crane operator. The boom tip is preferably let down close to the ground with an extended boom.
It is expedient for the re-reeving process with a let-down boom to secure the hoist rope to one or more securing means at the crane boom for safety reasons. The securing is preferably made before or shortly after the release of the fixing point of the hoist rope to the boom system. The hoist rope is released again before taking up the desired crane operation.
A fast and simple possibility can preferably be provided for a variable attachment of one or more additional elements to the boom, in particular to the boom tip. One or more boom elements can in particular be mounted to extend the boom to increase the useful boom length. The integration of other boom elements which provide additional functions at the boom system is, however, likewise conceivable. For example, individual elements or apparatus for the display of information can be attached to the boom tip. A combination of these elements with boom extensions is likewise conceivable.
The integration of one or more boom elements is facilitated by the letting down of the boom tip close to the ground. The boom can also be extended specifically for the luffing mode, which is not possible in the named fast and simple manner without any further effort in known trolley boom cranes due to the complexity of the trolley construction.
If one or more boom elements are mounted at the boom tip for the luffing mode, the hoist rope fixing point is released and is pulled out with the aid of a securing rope up to one of the additional boom elements, in particular up to the tip of the outer additional boom element. The securing rope is preferably guided from the outer tip of the outermost additional boom element up to the hoist rope fixing point for this purpose.
For the luffing mode, the hoist rope is expediently deflected by a deflection pulley attached to the additional boom element and is connected at the end side to the corresponding crane hook.
It is particularly advantageous if the rope reeving pulley is dismantled at the original boom during the trolley mode and is mounted at the corresponding additional boom element for the deflection of the hoist rope.
The hoist rope fixing point is preferably pulled up to the tip of the at least one additional boom element using a hand winch.
One or more sensors can detect the spatial geometry of the current crane configuration and can thus automatically recognize the planned crane mode, that is the luffing mode or trolley mode. The crane control can consequently work while taking account of the recognized crane mode and can release or carry out corresponding crane commands or functions.
The invention further relates to a crane, in particular to a revolving tower crane or to a mobile construction crane, having a luffable crane boom, in particular a luffing boom, and having a trolley arranged travelable at the crane boom. The proposed crane configuration allows the crane to be operated in a luffing mode, on the one hand, and in a trolley mode, on the other hand.
In accordance with the invention, the hoist rope of the crane is guided in the luffing mode via at least one deflection pulley at the crane boom, in particular at the boom tip, and is beaten up at the end side to a load hook or is latched thereto. The crane is characterized in accordance with the invention in that a one-line operation of the hoist rope is ensured during the luffing mode, whereas a multiple reeving of the hoist rope is necessary as a rule during the known trolley mode.
Certain advantages result from the single-line routing of the hoist rope during the luffing mode. For example, the position of the trolley is insignificant for the function of the crane in the luffing mode; a positioning close to the boom pivot-connection point is therefore possible. A larger hoist rope quantity is furthermore available by the single-line operation.
The crane in accordance with the invention advantageously moreover comprises means for carrying out the method in accordance with the invention or an advantageous embodiment of the method in accordance with the invention. The advantages and properties of the crane in accordance with the invention obviously correspond to those of the method in accordance with the invention so that a repeat description will be dispensed with at this point.
Further advantages and properties of the invention result from an embodiment described in more detail in the following drawings.